Brière is the marsh area to the north of the Loire estuary in France at its mouth on the Atlantic Ocean. The residents of Brière are called Briérons. The Brière marsh area includes a vast area of humid zones stretching from the Gulf of Morbihan and the estuary of the Vilaine to the north, to the salt marshes of Guérande to the west to the estuary of the Loire and the Lac de Grand-Lieu in the south. Peat used to be harvested here.